Meningococcal meningitis outbreaks caused by Neisseria meningitidis are responsible for significant morbidity and mortality in the African meningitis belt, a region stretching from Senegal to Ethiopia. Asymptomatic pharyngeal colonization with N. meningitidis, known as carriage, is relatively common compared to invasive disease, and carriers are the primary source of transmission. An affordable conjugate meningococcal serogroup A vaccine has been developed to reduce the burden of meningococcal disease, but it has not yet been introduced into the region. To interrupt transmission and prevent epidemic meningitis, the newly developed vaccine will need to prevent or reduce carriage. Prior to the introduction of this vaccine, studies are needed to further define the epidemiology and basic natural history of carriage in this context. In partnership with the Meningitis Carriage Consortium, an international collaborative effort to characterize the epidemiology of N. meningitidis carriage, and the Centre pour le Diveloppement des Vaccins (CVD-Mali) in Bamako, Mali, the main objective of this study is to investigate rates of acquisition and loss of carriage within households over time, to estimate the average duration of carriage, and to evaluate potential risk factors for carriage. In addition, the aim is to pilot test field and lab protocols for longitudinal follow-up of households in a developing country setting prior to introducing this study design in seven countries of the meningitis belt. To meet these Aims, we propose a household-based longitudinal study of N. meningitidis carriage with 12 months of follow-up. Households will be randomly sampled to identify those households with at least one carrier. Ultimately, 20 households with carriers will be enrolled in and visited monthly. At each visit, an oropharyngeal swab will be collected from all members of the household to determine carrier status and a questionnaire administered to assess potential risk factors. Swabs will be analyzed in the lab using bacteriological and molecular methods to determine the specific serogroup of the strain being carried and the relatedness between strains carried by household members. These data will allow investigators to assess changes in carrier status over time and to define the basic epidemiology of N. meningitidis carriage in the general population in Mali. This study is an important step towards understanding the dynamics of persistence and spread of N. meningitidis. This project will exert a substantive, powerful influence on the research field by laying the foundation for similar longitudinal studies to be carried out in seven countries. This proposed study will also provide baseline data for evaluating the direct and indirect effects of the new meningococcal serogroup A vaccine in Africa. There is a significant need to pilot test field and lab protocols to determine the feasibility and acceptability of longitudinal follow-up of carriers of N. meningitidis in this setting. PUBLIC HEALTH RELEVANCE: This proposed study is relevant to public health because it will further our understanding of the epidemiology and natural history of N. meningitidis carriage, which is one of the primary targets for reducing transmission and preventing outbreaks of invasive meningococcal disease in the African meningitis belt. Our aim is to provide necessary baseline longitudinal data about the average duration of carriage, rates of acquisition and loss, and potential risk factors for carriage within households. Knowledge about these characteristics and the ability to pilot test this design will contribute to the implementation of the same design in seven African countries, which will ultimately assist in the evaluation a new conjugate meningococcal serogroup A vaccine.